docs: def save_freesurfer_morph(filename, obj, face_count=0):
      '''
      save_freesurfer_morph(filename, obj) saves the given object using nibabel.freesurfer.io's
        write_morph_data function, and returns the given filename.
      '''
      fsio.write_morph_data(filename, obj, fnum=face_count)
      return filename